Breakdown Mechanisms in β-Ga₂O₃ Trench-MOS Schottky-Barrier Diodes

The breakdown mechanisms of >1kV β -Ga₂O₃ trench-MOS Schottky-barrier (SB) diodes (SBDs) are investigated during step-stressed voltage measurements. We demonstrate the use of current leakage noise to characterize leakage mechanisms. Comparing the normalized current noise characteristics of a set of trench-MOS SBDs to a metal-oxide-semiconductor capacitor (MOS-CAP) and a planar SBD test structure, the origin of two leakage mechanisms can be discerned. At low biases, leakage is dominated by barrier tunneling at the SB interface. At higher biases, non-reversible soft-breakdown events are observed, with a sharp increase in leakage current associated with breakdown at the oxide interface. Beyond these non-reversible soft-breakdown events, localized Al2O3 leakage paths dominate the leakage noise signature. Changes in the dominant leakage mechanism, under reverse bias stress, have implications for the voltage ratings and lifetimes of reduced surface electric field (RESURF) devices that incorporate oxide layers for enhanced breakdown fields.